The best feature that an instant messaging app can have is all of your friends using its service. The second best, arguably, is stickers. Taking advantage of the surprising popularity of these oversized emoticons, BlackBerry is beginning to add stickers into BBM. Sticker packs with names like "CosCat," "Gilbert’s Tales," and "Bubble Bot" will be sold directly within the app and contain around 20 to 25 images apiece. Some sticker packs may be available for free as well, including one that reworks existing BBM emoticons for the larger new medium.

BlackBerry says that BBM stickers are entering a limited beta today, but doesn't say how you'll be able to join in or when they'll roll out to everyone. BBM also recently added a number of features to Android and iOS as well, including voice calls, support for its Channels feature, location sharing, and attachments. BlackBerry may have severely limited BBM's user base by only opening it up to other platforms last year, but it's clearly moving quickly to make it a robust messaging option. Stickers will make it a lot more fun — now BlackBerry just needs to get people to use it.